Studies on the biosynthesis of immunoglobulin by short-term tissue cultures of normal and leukemic human peripheral blood lymphocytes will be continued. IN order to assess whether chronic lymphocytic leukemia (CLL) represents a clonal expansion of a single cell, the immunoglobulin synthesized by CLL lymphocytes will be analyzed by isoelectric focusing on polyacrylamide gels. Studies on the pathway of assembly of IgM immunoglobulin, analagous to those performed with IgM-producing plasma cells, will be undertaken by sizing intra- and extracellular immunoglobulin on sucrose density gradients Lactoperoxidase-catalyzed iodination of the surface immunoglobulin of CLLlymphocytes will be performed to label the IgG exogenously bound by IgM producing CLL lymphocytes. The kinetics of release of the iodinated IgG into the culture fluid will be analyzed, and the degree of heterogeneity of the bound IgG will be analyzed by isoelectric focusing to assess the functional significance of binding of exogenous immunoglobulin by CLL lymphocytes. Studies on the chemistry and biosynthesis of a novel component present in the serum of CLL patients but undetectable in normal serum will also be initiated.